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Stress and disease resilience differences related to emergence time for first feeding in farmed rainbow trout (Oncorhynchus mykiss)

Gesto, Manuel; Madsen, Lone; Andersen, Nikolaj R. and Jokumsen, Alfred (2018) Stress and disease resilience differences related to emergence time for first feeding in farmed rainbow trout (Oncorhynchus mykiss). [Forskelle i tilpasning til stress og sygdom i relation til tidspunkt for fødesøgnings adfærd hos opdrættede regnbueørred (Oncorhynchus mykiss).] Journal of Experimental Biology, XX (YY), a-b.

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Summary

Salmonid individuals show a relatively high variability in the time required to abandon the gravel nest where they hatch, the so-called "emergence time". Different behavioral and physiological traits have been shown to be associated to that emergence time in wild salmonids. In general, early- and late-emerging fish have traits resembling those of proactive and reactive stress coping styles, respectively. Proactive fish are considered to be more resilient to stress and probably to disease, so it was hypothesized that fish with different emergence time have different ability to resist repeated episodes of stress without suffering deleterious effects on their welfare or health status. In this study, rainbow trout eyed eggs were hatched and larvae were fractionated according to their emergence time (Early fraction: first 20 % of fish to emerge; Intermediate fraction: mid 20 %; Late fraction: last 20 %). When the fish were four months old, part of the fish were exposed to a daily repeated stress protocol for 15 days. The next day, both naïve and repeatedly-stressed fish were exposed to an acute stress challenge. Different plasma (cortisol, glucose, lactate) as well as CNS (serotonergic activity) stress markers were assessed to evaluate the stress resilience of the different fractions. Furthermore, an intraperitoneal infection challenge with Flavobacterium psychrophilum was carried out to assess the disease resilience of the different emergence fractions. Altogether, the results showed that fish from different fractions displayed different activation of the hypothalamus-pituitary-interrenal axis, pointing to a higher stress resilience in the fish with shorter emergence times. However, those differences were not reflected in the ability of the different fractions to grow and perform well in terms of growth, or in the ability to overcome the infection with the bacteria, which was similar for all the emergence fractions. This suggests that discriminating fish according to emergence time would probably have little effect in improving the performance and the welfare of farmed fish.


Summary translation

Hos laksefisk er der relativ stor individuel variation i tidspunktet for første fødesøgningsadfærd. Hos vilde laksefisk er blevet påvist en sammenhæng mellem swim-up adfærd og forskellige adfærdsmæssige og fysiologiske træk. Generelt har tidlig henholdsvis sen swim-up fisk træk som ligner henholdsvis proaktiv og reaktiv stress reaktions mønstre. Proaktive fisk er blevet anset for at være mere robuste i forhold til stress og sandsynligvis også sygdomme, og der blev derfor opstillet den hypotese, at fisk med forskellig swim-up tidspunkt havde forskellig evne til at modstå gentagne stress påvirkninger uden særlig påvirkning af deres velfærd og sundhedstilstand. I dette studie blev regnbueørred æg klækket og larverne blev fraktioneret i forhold til swim-up tidspunkt (Tidlig fraktion: første 20 % af swim-up fisk Mellem fraktion: mellemste 20 %; Sen fraktion: sidste 20 %). Da fiskene var 4 måneder gamle blev en andel af fiskene udsat for gentagen daglig stress i 15 dage. Den følgende dag blev både kontrol og de gentagen stressede fisk udsat for akut stress. Stress håndteringen i de forskellige grupper blev belyst ved analyse af plasma (cortisol, glucose, lactate) samt CNS (serotonergic activity) stress markører. Desuden blev der udført en intraperitoneal infektions challenge med Flavobacterium psychrophilum (YDS-bakterier) med henblik på at undersøge håndtering af sygdomsstress i de forskellige fraktioner. Samlet set viste resultaterne, at fisk fra de forskellige fraktioner udviste forskellig aktivering af hjernecentre (hypothalamus-pituitary-interrenal axis), der tydede på en højere grad af stress håndtering i fisk med første swim-up. Dog afspejlede disse forskelle sig ikke i de forskellige fraktioners performance (vækst eller evne til at modstå infektion med YDS bakterien). Disse resultater tyder således ikke på en sammenhæng mellem tidlig swim-up og bedre performance og velfærd hos opdrættet regnbueørred.

EPrint Type:Journal paper
Keywords:Stress; disease; resilience; aquaculture; emergence time; rainbow trout
Subjects: Animal husbandry > Health and welfare
Research affiliation: Denmark > Organic RDD 2 > RobustFish
DOI:10.1242/jeb.174623.
Deposited By: Jokumsen, Senior Advisory Scientist Alfred
ID Code:32863
Deposited On:05 Apr 2018 11:16
Last Modified:05 Apr 2018 11:16
Document Language:English
Status:Published
Refereed:Peer-reviewed and accepted

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